PHP superglobal variables, magic variables and magic methods

PHP has predefined 9 super global variables, 8 magic variables and 13 magic methods during design. These variables and functions can be used anywhere in the script without declaration. These variables and functions are frequently used in PHP development. These variables and functions can easily help us solve many problems. The following explains in detail the superglobal variables, magic variables and magic methods in PHP.

PHP super global variables (9)

　$GLOBALS　Storing variables in the global scope

　$_SERVER　Getting server-related information

　$_REQUEST　Getting parameters for POST and GET requests

　$_POST　Getting POST request parameters of the form

　$_GET　Get the GET request parameters of the form

　$_FILES　Get the variables of the uploaded file

　$_ENV　Get the array of server-side environment variables

　$_COOKIE　Browser cookie operation

　　　Set cookie: setcookie(name, value , expire, path, domain);

　　　　Get cookie: $_COOKIE["user"];

　　　Delete cookie: setcookie("user", "", time()-3600);//Set expiration time

　$ _SESSION Server-side session operations

　　　 Before using session, session_start() must be started with session_start()

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　ccotz\\'\'\'\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'s SESSION[" name"]);//Destroy a

　　　　session_destroy() and unset($_SESSION);//Destroy all sessions

PHP magic variables (8)

　__LINE__　 The current line number in the file.

　__FILE__　The full path and file name of the file. If used within an included file, returns the name of the included file.

　__DIR__　The directory where the file is located. If used within an included file, returns the directory where the included file is located.

　__FUNCTION__　 Constant returns the name of the function when it is defined

　 __CLASS__　 Constant returns the name of the class when it is defined (case-sensitive).

__TRAIT__ The name of Trait (new in PHP 5.4.0). Since PHP 5.4.0, PHP implements a method of code reuse called traits.

　__METHOD__　The method name of the class (newly added in PHP 5.0.0). Returns the name of the method as it was defined (case-sensitive).

　__NAMESPACE__　The name of the current namespace (case-sensitive). This constant is defined at compile time (new in PHP 5.3.0).

PHP magic methods (13)

　__construct()　 is called when instantiating an object. When __construct and a function with the class name and function name exist at the same time, __construct will be called and the other will not be called.

　__destruct()　 Called when an object is deleted or the object operation terminates.

　__call()　　 The object calls a method. If the method exists, it will be called directly; if it does not exist, the __call function will be called.

　__get()　　When reading the attributes of an object, if the attribute exists, the attribute value will be returned directly; if it does not exist, the __get function will be called.

　__set()　　When setting the attributes of an object, if the attribute exists, the value will be assigned directly; if it does not exist, the __set function will be called.

　__toString()　 Called when printing an object. Such as echo $obj; or print $obj;

　__clone()　　 Called when cloning an object. For example: $t=new Test();$t1=clone $t;

　__sleep()　　serialize was called before. If the object is relatively large and you want to delete a few things before serializing, you can consider this function.

　__wakeup()　 Called when unserialize to do some object initialization work.

　__isset()　 Called when checking whether an object's attributes exist. For example: isset($c->name).

　__unset()　 Called when unsetting a property of an object. For example: unset($c->name).

　__set_state()　Called when var_export is called. Use the return value of __set_state as the return value of var_export.

　__autoload()　 When instantiating an object, if the corresponding class does not exist, this method is called.